Update setup.rst with minor corrections [skip ci] (#4017)
Update setup.rst with minor corrections [skip ci] (#4017)

This PR updates `setup.rst` with a couple corrections and punctuation.
mrocklin/dask,mrocklin/dask,blaze/dask,ContinuumIO/dask,blaze/dask,jcrist/dask,jakirkham/dask,jakirkham/dask,dask/dask,ContinuumIO/dask,dask/dask,jcrist/dask